Abstract: A unique and extremely practical solar heater has been described which is particularly suited to the heating of swimming pools. The novelty of the system lies in the use of an extremely light-weight flexible unit of essentially all plastics construction which floats upon the surface of the pool and is easily removed therefrom, and which functions dually as a flat plate collector by virtue of water circulating through it during sunlight hours, and as an efficient insulator and vapor barrier for the pool surface. A number of such units are generally employed to cover most of the surface of a swimming pool, and are covered by a relatively thin plastic over-cover, preferably transparent and tinted an attractive color.